Weather Blog: Cool start to July & storm recap

Thank you for stopping by the Weather Watch 12 blog! The warmest month of the year in Milwaukee is getting off to a cool start. In today's blog we discuss cool temperatures and a warm-up, plus look back at recent severe storms.

Let's start with a beautiful sunrise photo from the Summerfest grounds Wednesday morning. I took this photo while doing live shots for WISN 12 News this Morning.

Comfortably cool weather will take hold through Thursday with high pressure returning to the Great Lakes. Temperatures will stay in the 60s today with more clouds than sun and some light showers from time to time. The WPC surface forecast map below is valid Thursday at 7am. With high pressure nearing Wisconsin sunshine is expected.

Temperatures will return to the 70s on the 4th of July with lots of sunshine. Don't forget sunscreen! Overall a beautiful day. The long holiday weekend will bring warmer temperatures and increasing humidity. The EURO computer model below is valid this Sunday. This shows southwest winds and very warm temperatures to close the holiday weekend. The threat of a shower or thunderstorm may creep back in the forecast late Sunday or on Monday. The warm and humid weather may extend into Monday.

Recent severe thunderstorms produced tornadoes, damaging winds and more heavy rain. Often times you hear me talk about 'radar indicated' when describing why a warning has been issued. Below are a couple of clear examples of how I used radar to keep viewers informed in recent days.

As severe thunderstorms hit southwest Wisconsin Sunday evening I took to Twitter @jnelsonweather to keep my followers in that part of the state safe. A tornado warning was in effect for parts of Grant and Iowa counties this evening.

Radar velocity helps in indicating wind speed and direction within a storm. If rotation is being indicated red and green will appear next to each other. The colors represent the motion/speed toward or away from the radar's location. The radar image at 10:24pm indicated two distinct areas of rotation. This is shown in the image below on the left.

The image on the right from 10:34pm Sunday evening shows correlation coefficient(CC). The CC serves well at discerning echoes of meteorological significance. The CC shows low values when the radar detects objects such as storm debris being blown through the air(non uniform pattern). When a very low CC value shows up near rotation on the radar, this is usually an indication of debris being shown by radar.

That was exactly the case Sunday evening in Iowa county as two tornadoes occurred, both EF-2 with winds of 111-135mph. The map below shows the two tornadoes near Dodgeville that correspond with the map above. There is also a tornado confirmed near Oregon in Dane county. Map below is courtesy of NWS.

The severe storms that hit southeast Wisconsin on Monday contained damaging winds, but this time no tornadoes were reported. Let's look at the velocity from around 6pm Monday evening. Winds of 60-65mph were being indicated by radar over Lake Country in Waukesha county. The velocity image below shows the most intense winds near and just east of Nashotah. The circle with a target is where I was located, at Arrowhead high school. The intense winds were moving northeast.

Unlike the velocity image shown above, this one had no red/green colors next to each other. A clear indication of straight line winds and not a tornado. The image below was another of many that I included in tweets in advance of the damaging winds hitting our area.

When the strong winds hit my location and nearby areas many large trees were downed. The evergreen tree below that was toppled was located about 3/4 mile from Arrowhead high school. The strong winds continues east-northeast resulting in trees and powerlines down in parts of Waukesha and Milwaukee counties.

A much needed break from severe weather is upon us, expect quiet weather to hold through much of the upcoming holiday weekend. Enjoy!

For the latest weather information watch WISN 12 News, and for updates throughout the day follow me on Twitter @jnelsonweather